Fundus and retinal imaging are important diagnostics in ophthalmology. Advanced imaging technologies now exist to detect tissue changes that occur due to retinal injuries not discernable with fundus photography. For example, optical coherence tomography (OCT) can provide depth-resolved images of ocular tissues approaching cellular resolution. The confocal scanning laser ophthalmoscope (SLO) also plays an important role in high-contrast visualization of thermal and other damage near sensitive retinal anatomy (e.g., the fovea).
OCT is an emerging technology for micrometer-scale, cross-sectional imaging of biological tissue and materials. A major application of OCT is ophthalmic imaging of the human retina in vivo. The Spectral-Domain OCT (SDOCT) improvement of the traditional time domain OCT (TDOCT) technique, known also as Fourier domain OCT (FDOCT), makes this technology suitable for real-time cross-sectional retinal imaging at video rate. At high speed, the need for vertical realignment of “A-scan” depth profiles is effectively eliminated across single B-scans, revealing a truer representation of retinal topography and the optic nerve head. Although B-scan image distortion by involuntary eye movement is reduced, transverse eye motion remains an issue for 3-D imaging and individual scan registration. Stabilized 3D OCT imaging can provide an en face fundus views for locating any given B-scan relative to retinal landmarks. Alternatively, simultaneous or interleaved live fundus imaging can also provide good retinal coordinates for a given B-scan, subject to the limitations of inter-frame eye motion.
The fusion of wide-field, line scanning laser ophthalmoscope (LSLO) retinal imaging with SDOCT imaging can enhance the clinician's ability to quickly assess pathologies in linked, complementary views with a simple, compact instrument. To make the ocular interface of future SDOCT systems more efficient, cost-effective, compact, and eventually field portable, neither complex motion stabilization systems nor opto-mechanical integration of secondary fundus cameras are desirable. Yet without precise knowledge of the OCT scan coordinates within the live fundus image to guide scan acquisition and interpretation, the diagnostic utility of this powerful imaging modality is limited.
The model for most clinical imaging systems to date has been the large stationary, desk-sized platforms with slit-lamp style human interface, bulky enclosure, numerous secondary optical or physical adjustment features, tethered power conditioning and signal processing units, computer, mouse and keyboard, and CRT monitor. These units generally require the subjects to adapt their posture to the instruments, rather than vice-versa. They typically combine the user interface and image acquisition functions with the image processing functions, the image analysis functions and the patient database. What is needed is an imaging system that can adapt to the patient, one where the operator, technician or medic can gather data, and an eye injury expert can provide analysis remotely based on the data recorded.